No Clear Winner In Race To Find Non-BPA Can Linings | February 11, 2013 Issue - Vol. 91 Issue 6 | Chemical & Engineering News
Volume 91 Issue 6 | pp. 24-25
Issue Date: February 11, 2013

No Clear Winner In Race To Find Non-BPA Can Linings

Chemical firms cook up new recipes, but none will work for all foods and beverages
Department: Business
Keywords: BPA, canned food, food packaging, endocrine disruptor
Credit: Shutterstock
Photo of open cans of food that show the inner can coating.
Credit: Shutterstock

In late January, California proposed, for the second time, to list bisphenol A as a cause of reproductive toxicity under a state law called Proposition 65. Although the maximum allowable dose would be too high to require warning labels on most products, such as food cans that are lined with BPA-based epoxy resins, the proposal adds another reason that people might want to avoid the chemical.

In the past decade, consumers and health experts have raised concerns about the use of BPA in food packaging. The molecule has a shape similar to estrogen’s and thus may act as an endocrine disrupter. The chemical industry and makers of metal food packaging contend that BPA is safe.

But for food companies, pleasing consumers is a high priority, and most are eager to move away from packaging based on BPA. Coating manufacturers and their suppliers are working overtime to find a replacement for the ubiquitous epoxies, which are made by reacting BPA with epichlorohydrin. A review of patent filings and regulatory approvals shows that dozens of substances are in the pipeline. They are being developed by paint firms including Valspar, PPG Industries, and AkzoNobel, and by chemical firms such as Eastman Chemical, Cytec Industries, and Dow Chemical.

The winning recipe or recipes need to meet high-performance requirements, because can coatings do double duty under difficult conditions. They protect the integrity of the can from effects of the food and protect the food from the steel or aluminum of the can.

Coatings must maintain an airtight seal, even under the high heat and pressure built up during sterilization. They must not chip, flake, or peel during handling—even if a can gets dinged. They must have minimal cost and avoid health and environmental impacts. The coating should not alter the taste or odor of the food. The most difficult hurdle for a can coating is working across different types of food and as a drop-in material in high-speed manufacturing lines.

Companies working on replacements for BPA-based epoxies are not keen to talk about product development efforts in this sensitive area. However, Jonathan Mason, associate R&D director at Dow, agreed to answer questions by e-mail. He summed up the challenge facing the industry this way: “The lowest-price, best-performing solution today is epoxy.” In addition, he predicted that no one formulation in the initial group of alternatives will work across all food and beverage types. Instead, a variety of new technologies will be required.

This viewpoint is echoed by outside experts who have evaluated alternative substances. “We could replace all BPA coatings today—but how much are consumers willing to pay, and what inconvenience will they accept?” asks Daniel F. Schmidt, associate professor of plastics engineering at the University of Massachusetts, Lowell. If lower-performing coatings are used, they may result in corrosion, shorter shelf life, and food poisoning. At the same time, Schmidt takes seriously concerns about the effect of endocrine-like chemicals on the body. “I personally think it does make sense to get rid of BPA in food cans,” he says.

Synthetic candidates to replace BPA-containing epoxies in can coatings fall largely into two main chemical categories: acrylics and polyester resins. But these base compounds can be blended with myriad other chemicals such as vinyls, urethanes, or specialty additives. And blends have been proposed that combine polyesters and acrylics; polyesters and urethanes; and even acrylics, vinyls, and polyesters. Plant-derived oleoresins have been used with low-acid foods such as beans. Making a durable coating also requires use of a cross-linker, which is another area of study.

Although most of the synthetic replacements are recipes using well-known raw materials, Eastman is proposing coatings based on a new monomer. TMCD, or 2,2,4,4-tetramethyl-1,3-cyclobutanediol, is an ingredient in Eastman’s Tritan copolyester, which has been used to replace polycarbonate, another BPA-based polymer.

None of these alternatives gets high marks in all categories of performance and safety. A recent review of can coatings for food and beverages illustrates why. For example, acrylics used in food-contact applications are brittle, and the common acrylic monomer ethyl acrylate has a noticeable odor in low quantities. Oleoresins don’t adhere well to metal substrates and do not resist corrosion when used with chemically reactive foods such as tomatoes. Polyesters can also fail when attacked by acidic foods (Int. J. Technol. Policy Manage., DOI: 10.1504/ijtpm.2013.050999).

Dow’s focus is on a coating that will prevent corrosion from high-acid foods. The company is working on a drop-in replacement for can manufacturers based on polyolefins applied as a liquid solution. “Polyolefins have been used in rigid, film, and flexible food packaging for over 30 years and have been shown to be both safe and effective,” Mason points out.

Chemical and coating companies know that any substitute they propose will be carefully scrutinized by watchdog groups. Schmidt, the plastics engineer, points out that phenolic compounds like those used to cross-link resins may also be implicated as endocrine disrupters. In addition, consumers wary of BPA are not likely to embrace vinyl-based replacements. And any compound similar to BPA, such as bisphenol S, will also be considered risky.

Schmidt, who like Eastman researchers is working to develop a can coating based on TMCD, says chemists’ hard work has resulted in some incremental improvements. “But I would be willing to bet that all of these alternatives are either lower performing, more expensive, or both, versus the usual BPA-based epoxies,” he says.


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Anahata Love (February 21, 2014 4:27 PM)
I know the weight of glass and the breakage factor add to the cost of food stored and shipped in it. But I have often found awesome organic foods that I would not mind paying the price to have them preserved in glass. It is such a travesty to have a food produced from it's beginnings right up to the preservation process by pure and organic means to then be placed in a toxic container where it stews until it is used. Maybe the scientists working on this problem need to be ones who are not locked into researching only plastic based liners?
Deb s (April 13, 2014 10:52 PM)
I am quite wary of the use of plasticizers and their hormone disruptive properties.
Frozen foods removed from the freezer, and packaged in plastics, can have a strong chemical odor when opened. Is there data, or mandated testing ,of chemical leakage from other plastic packaging and films, into foods? how do these chemicals affect the bone marrow and do they increase risk of lymphomas and leukemias like other chemicals are known to do?
I strongly prefer foods packaged in glass.
gary hodgkins (January 25, 2015 3:59 PM)
Glass makes so much sense. Many of us grew up on "canned' fruit and veggies put up in glass by our mothers. I would gladly pay more for this packaging.
Melody Bomgardner (February 2, 2015 10:13 AM)
There ARE other choices for food packaging than cans, including glass and laminated cartons. You may want to contact your favorite food brands and ask what their plans are, or advocate for your preferred packaging material. Any material that comes into contact with food must be approved for use by FDA - you can check the FDA website to learn more about those materials.
Dr.Doug Rasic (February 2, 2016 12:55 AM)
I am not sure that any of these "NEW" substances/Resins will not break up under certain conditions ( acidic packs, oily packs,high temperature/cooking etc).
Acrilyc resing have an odor issues, polyester poor resistance to acidic packs such as acetic acid,and who knows what will migrate out of those.
BPA is in very low concentrations in the can, there is MUCH more BPA in the food/Pack itself then in the coating itself. Many equipment can NOT detect BPA in the can coatings, as we are talking as PART per Billion.
Maybe my Grandma is right when she says "BETTER THE DEVIL YOU KNOW"
Georeg Ulrich (March 30, 2016 5:43 PM)
I believe that all states should have glass bottle return centers where glass can be recycled and if this is taken care canned food producers would be able to easily change to canning with glass jars instead of metal. Only a few states provide that there is compensation for recycling and that is a travesty when it concerns the earth's and mankinds environmental problems
w. b. heintz (April 27, 2016 5:41 PM)
All of the above comments miss the key point. Give up processed foods completely, canned or otherwise. Whole, fresh, organic produce is available all year round and there is no need
for grandmother's processing procedures today. Also, grow some of your own food, frequent the local
farmer's market and do your own cooking.
Miss Ann Thropist (August 23, 2016 7:50 AM)
..except that most of them have been packed or transported at some stage in some plastic containers or bags. And stupid humans will put their 'healthy' organic produce in plastic bags or containers in the fridge.
It's nothing for nothing in life.
If you're not going to grow your own, then you must pay the price for the convenience of not having to do the work.
So, enjoy the convenience and con't complain if you get cancer.
Pat (May 31, 2017 7:01 PM)
It's hard to look at that list of potential new can liners, and retain your appetite for the food that's inside that can. No one is ignorant enough to believe that the chemical lining that can, will not be absorbed into the food (even in some trace amount), over the period of time that it is in transportation, and sitting in warehouses or store shelves.
Try to test one of these foods inside such a can, to see if there are any trace amounts of that chemical-liner found within that food after it's been sitting in it for however long, and I bet the absorption of that chemical liner is inevitable.
Manufacturers may be looking at this problem from the wrong angle, and maybe better off re-inventing the container, instead of focusing on a liner.
Sure glass is the best, but is there a possibility of having a back-up to glass? ..that is lighter, more stable (not as breakable), less costly (or at least not as costly), but most importantly, just as safe as glass, and would not even require a liner to begin with? I believe where there is a will, there is a way, but unfortunately, (at least for now) manufacturers are focused on chemical liners, instead of the container itself.

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